Connection nodes are used for digital transmission networks of the "synchronous digital hierarchy" type (SDH). The connection nodes make it possible to switch multiplex signals to different connection paths.
According to CCITT recommendations G.707, G.708 and G.709, multiplex signals consist of so-called containers in which the signals to be transmitted are located. One or more channels are transmitted to each container. A supplemental signal (POH) is added to each container to turn it into a so-called virtual container (VC). A so-called head part (SOH) completes the virtual container (VC), converting it into a STM-N multiplex frame.
The connection nodes now make switching individual containers to a STM-N multiplex frame, or also between different STM-N multiplex frames, possible.
Such connection nodes find application in "plesiochronous" (nearly synchronous) transmission networks, or in transmission networks consisting of both plesiochronous and synchronous network components.
The switching network of such a connection node is known from EP 0,378,122 A1. For switching, the known switching network has switching groups that consist of a number of switching elements. Each switching element has a memory for the intermediate storage of data. The switching elements are arranged in lines and columns, where all switching elements of a line are connected with one data input of the switching group, and all switching elements of a column are connected with one data output of the switching group, and the same data are stored in each switching element of a line. Each switching element is connected to a joint memory, which transmits the read address to the switching element, and where the sequence of the channels to be read is determined in this manner. The columnar arrangement of the switching elements permits reading the data of each data input in each data output.
Thus, in the known switching network, because of the distribution of the channels of one frame to all outputs of the switching network, it is necessary for the data to be intermediately stored in as many memory elements as the switching network has data outputs. This requires large storage capacity and a correspondingly high cost for reading the memory, which is a particular disadvantage with high bit rate frequencies and/or parallel data processing.
The invention has therefore the task of producing a switching network of simple construction.